Groundwater discharge into streams plays a major role in the preservation of stream ecosystems. There were two complementary methods, both based on the use of the distributed temperature sensing technology, applied in a headwater catchment. Measurements allowed us to characterize the spatial and temporal patterns of groundwater discharge and quantify groundwater inflows into the stream, opening very promising perspectives for a novel characterization of the groundwater–stream interface.

We have all seen trees swaying in the wind, but did you know that this motion can teach us about ecology? We summarized tree motion data from many different studies and looked for similarities between trees. We found that the motion of trees in conifer forests is quite similar to each other, whereas open-grown trees and broadleaf forests show more variation. It has been suggested that additional damping or amplification of tree motion occurs at high wind speeds, but we found no evidence of this.

Groundwater is an underappreciated catalyst of environmental change in a warming Arctic. We provide evidence of how changing groundwater systems underpin surface changes in the north, and we argue for research and inclusion of cryohydrogeology, the study of groundwater in cold regions.

In Arctic fjord valleys, considerable amounts of methane may be stored below the permafrost and escape directly to the atmosphere through springs. A new conceptual model of how such springs form and persist is presented and confirmed by numerical modelling experiments: in uplifted Arctic valleys, freezing pressure induced at the permafrost base can drive the flow of groundwater to the surface through vents in frozen ground. This deserves attention as an emission pathway for greenhouse gasses.

In this work we present experimental results of a novel actively heated fiber-optic (AHFO) observational wind-probing technique. We utilized a controlled wind-tunnel setup to assess both the accuracy and precision of AHFO under a range of operational conditions (wind speed, angles of attack and temperature differences). AHFO has the potential to provide high-resolution distributed observations of wind speeds, allowing for better spatial characterization of fine-scale processes.

Most observations of the atmosphere are point observations, which only measure a small area around the sensor. This limitation creates problems for a number of disciplines, especially those that focus on how the surface and atmosphere exchange heat, mass, and momentum. We used distributed temperature sensing with fiber optics to demonstrate a key breakthrough in observing wind direction in a distributed way, i.e., not at a point, using small structures attached to the fiber-optic cables.

Recession analysis uses the receding streamflow following precipitation events to estimate watershed-average properties. Two methods for recession analysis use recession events individually or all events collectively. Using synthetic case studies, this paper shows that analyzing recessions collectively produces flawed interpretations. Moving forward, recession analysis using individual recessions should be used to describe the average and variability of watershed behavior.

Reaction rates of radiatively and chemically active trace species are influenced by the mobility of air contained within the snowpack. By measuring wind speed and the evolution of a tracer gas with in situ sensors over a 1 m horizontal grid, we found that inhomogeneities in a single snow layer enhanced air movement unevenly as wind speed increased. This result suggests small-scale variability in reaction rates that increases with wind speed and variability in snow permeability.

Intrinsic permeability of snow is an important parameter that regulates snow–atmosphere exchange. Current permeability measurements require specialized equipment for acquisition in the field and have increased variability with increasing snow heterogeneity. To facilitate a field-based, volume-averaged measure of permeability, we designed and assembled an acoustic permeameter. When using reticulated foam samples of known permeability, the mean relative error from known values was less than 20 %.

Fibre optic distributed temperature sensing allows one to measure temperature patterns along a fibre optic cable with resolutions down to 25 cm. In geosciences, we sometimes wrap the cable to a coil to measure temperature at even smaller scales. We show that coils with narrow bends affect the measured temperatures. This also holds for the object to which the coil is attached, when heated by solar radiation. We therefore recommend the necessity to carefully design such distributed temperature probes.

We present a new instrument for measuring surface runoff rates ranging from very low (~0.05L min-1) to high (300L min-1, with much higher rates possible depending on the device configuration). The device is economical, simple, rugged, accurate and requires little maintenance (the system is self-emptying and contains no moving parts). We have successfully used this instrument in long-term monitoring studies and expect that it will appeal to other scientists studying runoff processes.